Make NetLog::EventParameters RefCountedThreadSafe.
Make NetLog::EventParameters RefCountedThreadSafe.

This avoids a potential race condition in events logged
on other threads and then passed to the IO thread by a
ForwardingNetLog (Such as ProxyResolvers do).

BUG=64188
TEST=none

Review URL: http://codereview.chromium.org/5354001

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@67142 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser